Greetings from Sydney
Here's all I do on my L122
... (no Leslie)
1. Unplug the RCA cable from the Hammond's preamp out to the reverb / power amp.
2. Insert a 1 to 2 RCA splitter into the preamp out socket.
3. Plug 2 x male RCA to 1.4" mono cables into the RCA splitter on the preamp out.
4. Send one through a home made 12AU7, low milliamp valve guitar pre amp / distortion box (this one has no footswitch bypass so it's permanently on).
5. Plug the distortion box output into the left channel of a Behringer 1202 mixer and pan it hard left.
6. Plug the other RCA to 1/4" cable from the preamp RCA splitter into the other channel of the Behringer 1202 and pan it hard right.
7. Now I have one clean signal into the Behringer (right channel) and one dirty one (left channel).
8. Set the manual switches to ensemble, full organ, second and third harmonic, normal vibrato, vibrato chorus, pull the bass volume drawbar right out and leave the soft volume tab up.
9. Weigh down three keys on the upper manual, three on the bottom and one bass pedal.
10. Adjust the channel trim input gain on the two input channels on the Behringer mixer to the where the clip lights come on then back them off a notch.
11. Set the main slider on the Behringer mixer to the 0db position on its scale and adjust the individual channel volume pots until the left and right mixer led's light up the 0db level. Remove the weights from the keys and pedals.
12. Take the left and right Main Outs from the Behringer 1202 and put them into a guitar AB pedal, this allows me to switch between a clean sound and a dirty one at will.
13. Plug a 1/4" to RCA female cable into the output from the AB pedal and plug it back into the Hammond RCA preamp to reverb / power amp cable that was unplugged from the preamp at the beginning of the process.
14. The audio chain is now complete again but with a switchable / blendable clean and dirty channel and an extra gain boost stage between the Hammond preamp and the Hammond reverb/power amp. The little Hammond can now run louder, clean, dirty or blended than it can in it's ex factory state. All the organ options still run. I get an extra layer of volume control from the master slide on the Behringer mixer. If I want to blend the clean and the dirty signals I just adjust the panning on the clean and dirty channels mixer to taste. Adjust the distortion box controls to the level of distortion required for the dirty channel and check the mixer trim clip and master gain levels again. Adjust as necessary. If the clean channel starts to distort, just back off it's individual channel volume pot on the mixer until it stops.
15. If I want to run an extension amplifier I can take line outs from the Control Room outs from the Behringer mixer and use them. If I only want an extension amplifier and not the Hammond's internal one I only use the Control Room outs from the Behringer mixer and not the Main Outs that go back to the Hammond's reverb / power amp. If I want it to be balanced out for a big PA I just plug those Control Room out's into a dual DI box and leave the rest up to the FOH sound engineer.
16. If I want to go back to the ex factory state I just unplug the RCA splitter from the preamp out and plug the Hammond reverb power amp cable back in.
It works for me.
Cheers
Jed
Hammond L122
Roland VR760
Yamaha CS-30M